After dismantle which will take place this year, Radio Kaikan will be reborn as a 12 floor (10 above and 2 below ground level) fortress due to be complete in Spring 2014. For the time being, all tenants are relocating either to one of the 3 Radio Kaikan temporary buildings dotted around Akihabara or opening up new shop like Volks and Kotobukiya.
This map has 3 areas marked in red where the new buildings are located.